The Laser Interferometer Space Antenna (LISA) will explore the yet-uncharted millihertz band of the gravitational-wave (GW) spectrum in between the very low frequencies probed by pulsar timing arrays and the kilohertz window accessible to ground-based observatories. LISA's adoption is scheduled for early 2024 and data analysis methods are well underway, given the novelty and complexity of the expected data. The GalaxyFIT project aims at designing methods that simultaneously measure and describe the LISA noise, the gravitational-wave signals from thousands of sources, plus gravitational-wave backgrounds from astrophysical and cosmological sources. Integrated methods starting from non-ideal interferometric data all the way to data quality assessments of partially resolved sources are a necessity for LISA to reach its science objectives. GalaxyFIT will focus on ultracompact binary sources in the Milky Way where thousands of sources will be individually resolved and many more will result in an unresolved background, dominating the instrument noise and hampering the detection of a cosmological gravitational wave background. Specifically, GalaxyFIT will establish improved methods for detection and characterization of sources in the presence of non-ideal instrumental noise, and assess the impacts of different data quality cuts on astrophysical inference (measurement of Galactic structure parameters and features in the distributions of the binaries) and the measurement of a cosmological background. GalaxyFIT gathers experts on the LISA instrument, data analysis and astrophysical interpretation and aims to address many of the important data analysis and scientific goals that France has assumed for the LISA Mission, and pave the way for maximised scientific output with the LISA data. GalaxyFIT will also train a new generation of scientists towards this goal.

The lowest metallicity stars are also the oldest ones and they carry the imprint of the first supernovae. Since the very first stars are likely short-lived and inaccessible to us, the lowest metallicity stars are also those that can inform us most on the first generation of stars, how they enriched their environment, and produced the first structures that, through hierarchical formation, built up the primordial constituents of the galaxies we observe today. These stars are exceedingly rare and few of them are known today. In order to efficiently improve on this situation, we have put in place the Pristine international collaboration. Focussed around a wide narrow-band photometric survey conducted at the Canada-France-Hawaii Telescope and a large dedicated spectroscopic campaign, Pristine is many times more efficient than previous attempts at finding the precious low-metallicity stars. From the detailed study of these stars, we will: hunt for the most extreme low-metallicity stars; place constraints on star formation during the earliest epoch of the universe; reliably unveil the properties of the faintest known dwarf galaxies that orbit the Milky Way and are promising cosmological probes; decompose the Milky Way into its main components to place our Galaxy in the global context of galaxy formation and evolution; deconstruct the stellar halo of the Milky Way into its constituent substructures, which will then be used to constrain the mass and shape of the Milky's Way potential. In order to reliably achieve these significant goals, we request funding to support Pristine in France and ensure the project is staffed adequately to yield high-impact scientific returns in the field of very low metallicity stars. Our team is built around experts of the field in Nice (OCA/Lagrange), Paris (GEPI), and Strasbourg (Observatoire astronomique de Strasbourg) and represents a large part of the full Pristine collaboration. To complement this team, we ask for funding for a PhD student and two postdoctoral researchers who will be spread over the three French nodes of our project, along with funds to support the team and secure the visibility and active partnership of the French team members within the full international Pristine collaboration. We wish to emphasize that the effort already invested by the current team members into preparing the survey (successful telescope time proposals, data acquisition, reduction, and calibration, start of the spectroscopic follow-up campaign) means that the Pristine project is a low risk but high return project if it were to be supported by the ANR. It builds on large facilities and surveys with a significant French involvement (CFHT, Gaia, WEAVE) and it promises numerous high impact papers to be published in the high-visibility fields of Galactic archaeology and near-field cosmology in which France is a world leader.

We propose a development of infrared laser (operating at ~ 1.5 u m) with high frequency stability, locked to an hyperfine transitions of molecular iodine near 515 nm, after frequency tripling. The targeted frequency stability is better than 10-14 t -1 / 2. The experimental device is designed very compact, potentially compatible with space applications. The expected frequency stability is higher than any other laser in the optical domain stabilized by the saturated absorption technique. Lasers stabilized to optical cavities with temperature regulated offer frequency stabilities certainly more significant performance up to a few seconds if integration time, but require a more severe thermal and seismic environment. The frequency stability of STABI2 could be transferred, in the microwave domain with a performance of at least one order of magnitude higher than the hydrogen maser, for integration timesup to about 100 seconds. Furthermore, the use of masers is more delicate in case of on board / space.experiments Compared to commercial Rb or Cs clocks involved in space programs such as GPS or Galileo programs, the expected performance for STABI2 are 100 to 1000 times higher.